Update to version 1.3.
Reworked `atmos.retries.EventMonitor.PrintEvents`:

 - Converted `PrintEvents` into a trait and extracted two concrete
subtypes, `PrintEventsWithStream` and `PrintEventsWithWriter`.

 - Deprecated the use of booleans to signal whether a stack trace should
be printed for a particular event. The booleans are replaced by
`PrintEvents.PrintAction`, a `sealed trait` / `case object` enumeration
capable of representing any number of printing strategies.
Modified the retry DSL to support concise configuration of print actions
on event monitors derived from print streams and print writers.
Reworked `atmos.retries.EventMonitor.LogEvents`:

 - Converted `LogEvents` into a trait and extracted the concrete
subtype `LogEventsWithJava`.

 - Deprecated the use of log levels to describe behavior when called
with a particular event. The levels are replaced by
`LogEvents.LogAction`, a `sealed trait` / `case object` enumeration
capable of representing any number of logging strategies.
Reworked the Slf4j support in `atmos.retries.EventMonitor`:

 - Created `LogEventsWithSlf4j` as a subtype of `LogEvents`.

 - Converted `LogEventsToSlf4j` into a deprecated collection of aliases
to aspects of `LogEventsWithSlf4j`.

 - Deprecated the use of log levels to describe behavior when called
with a particular event, replacing them with `LogEvents.LogAction`.
Modified the retry DSL to support concise configuration of log actions
on event monitors derived from Java loggers and Slf4j loggers.
Restructured the mocking infrastructure for the event monitor tests.
Added support for asynchronous monitoring with Akka to `atmos.retries`.
Release version 1.3.